Revolutionary Propeller Design

 

I have talked about propellers and propeller design before, here and here.  In fact I proposed a new propeller design with a circular rim, but this revolutionary design  takes it a huge step further.  

Called a 'toroidal propeller', this design claims to eliminate tip vortices, consequently delivering a 20% increase in efficiency, and a huge decrease in noise.  Tho the article seems to be more focused on the application of the design to drone propellers (because drones and quadracopters are new, hip, and cool), it does mention marine applications.

And speaking of marine applications, when you are below decks and a boat passes by, you are certain to hear him - his prop makes a lot of noise in the water, and it is conveyed to your hull where you hear it.  Submarines have spent fortunes trying to eliminate prop noise because this noise carries a long way in the water and frustrates stealthy operation.  Expect these props to be refitted to all current and new submarines.

For now, if you want one for your boat, expect to pay approximately 10X the cost of a conventional prop, but this cost should come down significantly over the next few years, as the design gets adopted widely.

Revolutionary Propeller Design

Mizzen Rain Hood

Because our mizzenmast is stepped inside the cockpit, the cockpit enclosure must by necessity allow for the penetration of the mast.  In an attempt to minimize the amount of rainwater that enters the cockpit via the mast, the enclosure has a "sock" that goes up the mast a little ways and is tied around it.  Undoubtedly it stops most rain drainage, but a still significant amount gets into the cockpit, annoyingly to wet our trousers when we sit down.

An improved solution was called for.

The problem, in the rain, no less.

My first attempt was a simple, straight strip of vinyl cloth, mightily stretched around the cross section of the mast.  For obvious reasons, tho I was able to make it work, it failed to meet my aesthetics criteria.  (That is aluminum tape - I have extolled it's virtues before...)

First attempt: sloppy

The first reason a straight strip of vinyl failed to conform easily is that the mizzen mast is not a round cross section.  And the second is that the bottom of the strip had to accommodate a larger diameter than the top, due to the presence of the top seam of the sock.

Mizzenmast cross section

Well, this obviously called for the application of the lesson learned in Making a Mast Boot, with a minor modification.

First, we need to have a tapered hood, smaller at the top than at the bottom in order to accommodate the sock. I decided that tho the sock was about 1/4" thick (1/2", counting both sides), I should make the hood slightly larger so that the sock could easily fit up inside the hood, and to accommodate the place where the ends of the sock overlapped. I chose to make the bottom of the hood 3/8" larger on a side, or 3/4", counting both sides.  So, the tapered section needed to have a diameter of 3.75" at the top, and 4.5" at the bottom.

Next, the mast cross section is not round. Instead, I chose to view it as two half-round sections, joined by two straight sections.

Since I already screwed up one piece of vinyl, I decided to make a paper pattern this time, using freezer paper (eh, it was what we had...). Using the instructions in the mast boot post, I traced out an arc of sufficient length to supply pieces for both the front and rear of the mast. The arc for the rear of the mast I made extra long so that the ends would be able to overlap, and then I cut this piece in two. Then I cut out a couple of straight sections to accommodate the sides of the mast.

When joined together, the pieces looked like this:

From left to right, this is:

• Rear piece, extra long
• Side piece
• Front piece
• Side piece
• Rear piece, extra long

The change in shape seems kind of subtle, but the paper pattern fit the mast perfectly when I tested it.

Taped to back of the vinyl

After testing the pattern, I taped it to the back side of the vinyl, traced its outline and cut it out:

Taa Daa!

And... DONE!

And now because the hood is tapered, if I need to remove the sock I will not need to disturb the hood because I will be able to slide the sock up under the hood when reinstalling it.

Mizzen Rain Hood

Recursive Maintenance Continues

Maintenance recursiveness continues.

Being unable to budge the stubs left from grinding off the bolt heads, the only remedy was to remove the exhaust manifold/cooler to provide access for more drastic treatment of the bolt remainders than I could bring to bear with it in situ.

But...  before removing the exhaust manifold/cooler I had to drain both the antifreeze treated fresh water and the seawater from it.  This posed a problem because the genset and the heat pump share a thru hull, strainer and feed line.  Because it is still too cool here to do without the heat pump, I needed to install a shutoff valve in the genset seawater feed.

Genset seawater feed shutoff valve

This had it's own set of problems, first of which was a trip up into town to get some fittings.  Of course.  Despite the fact that I have a huge number of fittings aboard, none of them were suitable.  Then shut down the heat pump, close the seacock, cut the hose and clean up the mess from the drainage.  Finally, install the valve.

Draining the manifold/cooler

Now it was possible to drain the manifold.  Because Yanmar provided both drain petcocks and even drain hoses on the 2GMF, this was a clean job. 

And finally, removal of the now empty manifold was quite straightforward.

It turned out that the bolt stub removal was also easy...  because I took the manifold to Gustav at EngineTec here in Anacortes (highly recommended by Jason, and now I can add my enthusiastic recommendation as well).  An hour after I had dropped it off, Gustav called me telling me it was ready for pickup.  I barely had time to finish a post removal celebratory beer!

All I lack for reassembly is the gasket that goes between the manifold and the engine - currently on order.

---

I lay the blame for this incident at the feet of Kohler, the genset manufacturer.  Kohler adapted the Yanmar 2GMF to power the generator.  When they did so, one of the changes they had to make (in addition to relocating the oil filter) was to reorient the exhaust elbow.  The Yanmar elbow points straight down - that would have interfered with the generator body.

Kohler tilted the elbow to the right

So Kohler cut the elbow pipe off the flange and rewelded it at an angle to clear the generator body.  So far, so good.

The problem was that they made a dog's breakfast of it.  When the pipe was rewelded to the flange, the flange warped, making a seal against the manifold completely impossible.  Rather than redoing the weld, perhaps on a fresh, heavier flange, Kohler sealed the 1/8" gap using JB Weld or something similar applied to the manifold, and then to make sure, they installed two gaskets.  This all became obvious when I was able to inspect the manifold, and when I removed the gaskets and exposed the JB Weld (or whatever) on the manifold flange.  This crappy jury rig held for a while... perhaps 400 engine hours.  And then the leakage started.

Yanmar: 1
Kohler:   0


Previous post in this series

Next post in this series

Recursive Maintenance Continues

Dickenson Heater Maintenance

Dickenson Diesel-fired Heater

Have one of these?

Is the flame getting smaller and smaller over the years?

If so, eventually it will need to be cleaned - estimated MTB cleanings is about 15 years.  Diesel fuel is not quite free of ash - so ash will accumulate in the pot.  But more importantly, the diesel cokes out from the heat of the burner, leaving behind deposits of carbon.  These accumulate in the bottom of the pot.

But even more importantly than that, the carbon also accumulates in the fuel entrance to the pot, at its center bottom.  The feed from the float tank to the pot is strictly by gravity, with the head driving the flow only a couple of inches...  it doesn't take much to significantly decrease the flow when there is only this tiny pressure to drive it.
 
Thankfully, Dickenson anticipated this, and provided an easy port for cleaning.

If you look at the fitting where the diesel enters the pot (look from the bottom of the heater), you will see that instead of an elbow (which would have sufficed), Dickenson used a tee.  If you remove the plug from the bottom of the tee (watch out, some diesel will escape - have a container under the fitting when you remove the plug), you will find that you can push a typical Phillips screwdriver up thru the tee and into the pot.  This will clear out any coked out diesel or ash that has accumulated in the feed and entrance to the pot.

Next, you should also remove the copper pipe which leads from the float tank to the tee and clean it - some carbon may either have accumulated in it where it attaches to the tee, or may have been pushed into the pipe when the screwdriver was used to clean out the tee.


(Yeah, I know I am talking about heater maintenance in July, but: PNW)

Dickenson Heater Maintenance

Dodger? Why Not?

If you take a walk down any given dock here in the PNW, you will notice that virtually all the sailboats over about 30 feet long will have dodgers (except racing boats of course, but they are a different breed).  And except for a few obviously home-made ones, they are constructed of stainless tubing and canvas.

Have you asked yourself, "Why is this?"  I have.

They are made from stainless tubing and canvas because that is what the aftermarket can most easily produce to custom fit the broad variety of boats.  But these dodgers are not particularly sturdy and the canvas ages out over a decade or so.  And they are all add-ons, and they look it.

Why are these apparently universally desirable items left to the aftermarket to produce?  Why don't the boat manufacturers produce boats with designed-in, molded-in fiberglass dodgers?  If sailboats were cars, the auto manufacturers would be selling them without windshields.  And the aftermarket would be producing vinyl windshields that slowly decayed in the weather.

Question to my readers:  I have been in other parts of the coastal US but wasn't paying attention to the dodger issue.  Is this a universal trend in both temperate and tropical climates?  (I am virtually certain that all ocean-going cruising sailboats have dodgers.)

So. here's the challenge that I issue to Catalina, Hunter, Beneteau, Jeanneau, Morris, Hinkley, etc:

Design and produce sailboat decks with graceful, proportional, integral, fiberglass dodgers.  Dodgers that don't look like clumsy add-ons.

If not on all the boats you sell, then at least offer dodgers as an option.  If you don't try to price gouge on the dodger option, I think you will see that almost all the boats you sell will be ordered with the dodger option.

Come on.  I dare you.

---

Here's an example that anchored next to us today...  Doesn't that look nice?

Dodger? Why Not?

What wind generators ought to look like

A recent craigslist ad here in Seattle really caught my eye (it may not be there by the time this gets published, but if you are interested, let me know).  The ad offered a wind generator, but not like any I had ever seen.  The generator was manufactured by BalMar, a well-respected manufacturer of marine alternators and regulators.  And when I say local, I do mean local - BalMar is here in Ballard (I suspect that BalMar is a contraction of 'Ballard Marine').  A web search did not turn up any references to it, so it is apparently out of manufacture, sadly.

Now why was I so intrigued by it?

Well, first, a wind generator would seem to be a natural fit for an alternator manufacturer like BalMar.  And based on our experience with their other products, I'd expect that this thing is bullet-proof.

But more importantly, look at this:

It has self-adjusting variable pitch blades!  See those lead balls?  The faster the hub spins, the more they are thrown out, rotating the blades, changing their pitch.  The movement is resisted by the spring on the axle; adjusting the spring tension adjusts the rate of pitch change with RPM.

Why is this a big deal?  Because whatever pitch is set by the manufacturer of any fixed-pitch design (and that's all of them, I think...  somebody prove me wrong), it is really only optimal for a single wind speed.  And here is the proof of the pudding:  Virtually all current wind generators are just starting to turn at 10 mph.  This one, however, starts to deliver power at 5 mph, and produces 187 amp-hours a day at 12 mph.

And in high winds, it self-feathers to prevent overspeed.  Wow. 

Here is a view of the hub from the side:

As you can see, BalMar has fixed the 'rotor' portion of the alternator to the base plate, meaning that there are no slip rings.  The wiring just attaches directly to the coil.  The actual rotor (it would by the 'stator' in a conventional alternator) consists of a series of permanent magnets embedded in the white rotating hub.  And the hub is provided with fins to generate a flow of cooling air.  BalMar seems to have a well-thought out mature design here.

Huh.  So why aren't all contemporary wind generators derivatives of this design?  Well perhaps because it was sold for over $1000 more than 20 years ago.  In today's market, a $1000 generator would be at the high end.  Twenty years ago? 

Sadly, the adequate is often the enemy of the superior.

What wind generators ought to look like

Gotcha.

Today there was a most important convergence: It was not raining, and I was home while it was light. So I took another look at the mast boot.

Having given up on everything else, I cut a new one. Because I had the old one, I didn't have to go thru the patterning exercise - I just traced the old one onto the Naugahyde and cut it out. But first, of course, I had to pull the old one. It was instructive.

Here's the inside of the old one, showing clearly where water had been coming in. (Because of the way I laid it out in the cockpit, that's the bottom of the boot at the top of the picture.)  There are a couple of (dried) streams to the left in the picture, and one gigantic wet stream to the right of center in the picture.  When it was installed, this was at the back, where the sail track is on the mast - a tough place to seal.

The smoking gun

And look what I saw when I turned up the edge and looked closely at the boot where it went over the track.  Yep, the vinyl coating on the fabric had cracked, twice.

Some interesting gel-life growing inside the old boot

---

Update:

Looks like someone is running a hose
on the deck above, doesn't it?

And wouldn't you know?  Mother Nature delivers a test storm not long after I get the new boot installed.  Perfect timing... and it's not just any storm - in fact it is a deluge of Biblical proportions - any minute now I expect to see pairs of animals lining  up out there on the dock.  It's been going on now for 24 hours, and there is no end in sight.

So far?  One drop. 

Yeah.

---

Update #2:

Sunny and dry today (but cold).  This allowed me to inspect the new mast boot more closely than I was able to during and immediately after installation.  What I found was incomplete adhesion of the polysulphide I had used to seal the seam where the ends overlapped on the boot.

Drop explained.

And fixed.  (Replaced the polysulphide with 3M 5200.)

---

Previous post in this series.

Gotcha.

Imagination

imag·i·na·tion: n.  \i-ˌma-jə-ˈnā-shən\  The ability to look at a pile of shop scraps, and see a battleship.

Credit for this imaginative bit of naval architecture goes to Zak, who lives on s/v Ghost, across the dock from us. 

Imagination

Internal or external? Lead or iron?

Except for the smallest ones, monohull sailboats (you multihull readers can skip this post) universally have a keel on their bottoms.  They carry this device around with them because:

• It helps to keep the boat from sliding sideways when the wind is not taken directly astern, and
• it keeps the boat from tipping over when the sails are full of wind.

Today, I'd like to talk about the second item: keeping the boat from tipping over.  In naval architecture, the boat's ability to resist being tipped is called her "righting moment". 

Old sailing ships used rocks, held in the bottom of the bilge, as ballast.  When they took on cargo, some of the ballast was jettisoned because the cargo held below the waterline would provide the righting moment, and because the ships were designed to carry cargo, after all, not rocks.  (This led to the ballast spoils areas in many harbors that were heavily used in the 18th and 19th centuries.)

Modern sailboats have moved the ballast outside the boat, lower, where it can have a greater effect.  Like the big kid and the little kid on the teeter-totter (have these all been removed from playgrounds?  What will we use for the illustrative analogy in the future?), the more weight and the deeper it is suspended below the boat, the better: the greater the righting moment.  This started with shaped blocks of lead bolted to the bottom of the keel in full-keeled boats.  But it has evolved from there.

Internal or external?

For a fin-keeled boat, there is really only one choice here:  the keel is a shaped piece of metal bolted onto the boat's bottom.  It is an external keel.

But for a modern fiberglass hull which is designed as modified- or full-keeled, a second choice is possible:  internal ballast.  In this design, the shape of the keel is part of the fiberglass molding of the hull - the keel is molded as part of the hull.  And then the ballast is added to the inside of the molding.  Typically, this is as metal shot combined with resin in a cement mixer and then poured into the keel.  But it can also be done using shaped pieces of metal laid up in the interior of the keel and then encapsulated with resin.

• Internal keel pros:
• There are no keelbolts to worry about.  Short of complete destruction of the hull, the keel simply cannot drop off the boat as some external keels have famously done.  
• Maintenance of a water-tight seal between the keel and the hull is unnecessary.
• In a collision with a hard object, there is no fear of loosening the hull-keel joint.
• External keel pros:
• In a collision with a hard object, it is the keel which makes contact, not the hull.  If the keel is a soft metal like lead, deformation of the keel at the point of impact will absorb a portion of the energy.
• Because the void space of uniform-sized shot is 33%, the density of the poured shot keel will be considerably less than the solid metal.  Therefore the solid metal keel of equivalent shape will have a greater righting moment than an internal keel made from poured shot.  This advantage is considerably less if shaped metal pieces are used. 
  
  (Question:  Has any manufacturer explored the use of a range of shot sizes, designed to reduce the void percentage?  Concrete manufacturers have been doing this with the aggregates they use for centuries.  Seems like a simple improvement.)

Until some more exotic material is used (depleted uranium anyone?), keels will be made of either lead or iron. Both have advantages:

• Iron keel pros:
• Iron is a lot cheaper than lead
• For a steel boat, there is less galvanic potential between an iron keel and the hull than there is with a lead keel.
• Lead keel pros:
• Lead is denser than iron. This means that for equivalent shapes, the lead keel will have considerably greater righting moment.
• Lead does not corrode in seawater;  tedious and frequent scraping, sandblasting and painting of the keel is not needed.  In fact, other than for protection against freeloading sea life, painting of a lead keel is completely unnecessary.
• Lead does not corrode in seawater;  iron does.  In fact iron swells as it corrodes - that is, iron oxide is greater in volume than the iron from whence it came.  Therefore leakage is a serious problem for internal iron ballast, since the incoming seawater will corrode it and eventually cause the keel structure to burst.
• Already mentioned above:  An external lead keel will absorb a portion of the impact energy in a collision with an underwater object.  An iron keel will convey essentially all of that energy to the keelbolts and the hull at the top aft end of the keel.

This is a lot to consider.  When we were in our boat search, I boiled it all down to an ordered list of preferences:

1. Internal lead
2. External lead
3. External iron
4. Internal iron

As it turns out, Eolian's keel is internal lead.

But as any of you who have gone thru a boat search already knows, the emotional tug that a boat has on you overrules almost any of the analytical studies that you might have prepared beforehand.

At least it did for us.  So I guess we are just lucky...  but hey, this makes a nice rationalization, don't you think?

Internal or external? Lead or iron?

Winged keels?

If you didn't read that title carefully, you saw "winged heels" and are probably visualizing Mercury's boots.

But that's not what I want to talk about.  Instead I want to discuss winged keels.  I mean what is the big deal, after all?  Sure, they're modern, sure they're cool, and "every boat must have one".  But why, exactly?

It's all about end effects.

Huh?

OK, now I have to build something in your mind here.  Please give me some latitude and play along... Imagine an airplane wing.  Regardless of which theory you consider to describe how it holds the airplane up in the air, all the theories condense to the singular fact that there is lower pressure on top of the wing than on the bottom.  The airplane is held up by suction.  So what keeps the high pressure air under the wing from just flowing up into the low pressure area above the wing?  Well, on the leading and trailing edges of the wing, it is momentum - that wing is moving right along, and the air at the front and rear of the wing just doesn't have a chance to flow "upstream" to the low pressure area.

But what about at the ends of the wing?  Well, at the inboard end, there is the fuselage in the way.  Ah, but at the outboard end, there is... nothing.  And air does indeed flow up from under the wing around the end to the top.  This is the source of the "wingtip vortices" that cause the spacing out of flights at airports.

So, if you were an aeronautical engineer, how might you stop this flow around the end of the wing?  Well, you might put up a fence.  On the end of the wing.  In point of fact, this is exactly what is done on modern airliners.

OK.  So enough about airplanes... but hold that thought.  The keel of a sailboat is amazingly similar to an airplane wing.  It is "flying" thru the water, and is required to provide lift, to keep the boat from sliding downwind.  The analogy is really very good.  So then, what keeps the water from flowing over the bottom end of the keel, from the high pressure side to the low pressure side?  Nothing...

Thus enter the winged keel... put up a fence.  However, since each side of the keel is alternately the high pressure side and then the low pressure side as you tack, the keel has to have a fence on both sides,  explaining the now-familiar shape.

The design is so effective that significantly less ballast is required, the force being replaced with more effective lift.  Thus the weight of the keel can be reduced.  And the wings serve as a good place to stash lead, down there at the very bottom of the keel, so the draft of the keel can be reduced.  And then, since everything in nautical design is connected to everything else,  the wetted surface of the boat is decreased because less total weight is being carried.  And the boat goes faster.

It really is a good idea.

So then why then did winged keels take so long to appear?

See the First and Second Corollaries of Salnick's First Law.

Winged keels?

Boarding ladders

One of the things that the Previous Owner did well on Eolian was the design and installation of our boarding lader.  Eolian has a lot of freeboard.  There is no way, for example, that you are going to board her from a dinghy without some kind of ladder.

It is not uncommon for boats with lots of freeboard to have boarding ladders.  The question always is: "Where do I put this thing when I am not using it?"  It is not an easy question to answer.

If you use the old aluminum folding standby, you can just store it on deck or against the lifelines.  Best to tie it down somehow, tho.

The Force 50's (this is Ghost) came with a wonderful traditional boarding stairs, that fold up and tie to the outside of the lifelines underway.  They are completely adjustable as to height - right down to the water, and make a great platform from which to board a kayak at anchor.

Cooper 416's come with a wonderful heavy teak ladder, which folds in half. 

















Eolian's Previous Owner (and I give him all the credit here) came up with a wonderful idea:

Fabricated out of stainless tubing large enough to be comfortable to bare feet, these are permanently bolted thru her hull.  There is a nut welded to the outside of the large washer (that is, inside the tubing), and a bolt goes thru the hull and engages the nut.  The large surface area of the washers provide the necessary stability.  And the bolt is sized to be more than adequate to support a fully mature male human being, but yet small enough to shear off and prevent hull damage should the step meet up with an immovable object - say, a dock (don't ask).   Yes, on a starboard tack, one or two steps may be submerged, adding a little drag.  But on a boat of Eolian's size, it doesn't account for much.

But best of all, we don't have to store them, and they are always ready for use.

---

Christian asked for additional detail on the steps - The best I can do here Christian is to put up this engineering sketch for the steps which was in the ship's papers:

Boarding ladders

How To Cut a Mast Boot

(Those of you with deck-stepped masts can skip this post. )

A keel-stepped mast must pass thru the deck. Where it does so, some kind of seal must be made to prevent a deluge of rain water from running down the mast into the cabin. Traditionally, this has been accomplished with a mast boot - a piece of flexible, waterproof material which covers the deck penetration. It is a simple, low-tech solution, one that has withstood the test of time. But: how to cut the fabric so that it drapes smoothly from the mast down to the deck?

It's not hard. Here's how:

To begin, you will need three dimensions:

• The circumference of the mast. Let's call this 'm'.
• The circumference of the raised deck ring onto which the bottom of the boot will be clamped. We'll call this 'd'.
• The height up the mast, measured from the deck, that the boot is to extend. Note that what follows is based on geometry that assumes that the deck ring and the mast have circular cross-sections. If yours is not (and it probably isn't), then add an inch or so to the desired height to allow for some final trimming. We'll call this 'h'.

Make these measurements and write them down.

Now, we need to do a little math - get out your calculator. We need the diameters of the mast and the deck ring:

• D_m = m / 3.1416
• D_d = d / 3.1416

Make these calculations, and write the results down.

You will be cutting out a shape that looks like this. We already have 'h', so all that we need now is R1 and R2.

To get R1, we need to do a little more math, using the numbers we have prepared above. Use this formula:

R1 = (h * D_d) / (D_d - D_m)

That is, multiply h by the diameter of the deck ring, and then divide the resulting number by the difference between the diameter of the deck ring and the diameter of the mast.

R2 is much easier:

R2 = R1 - h

With R1 and R2, you are prepared to lay out the pattern on a piece of suitable material (we used white naugahyde purchased from a local fabric store). You will find that R1 and R2 will turn out to be pretty long - you will probably need to do the layout out on the dock. Mark the pivot point on the dock, and set some weights on the fabric (wrong side up) at the right distance. Then make a series of marks using a tape measure at distance R1 from the pivot. Similarly, make a second series of marks at R2.

Connect the marks with smooth curves, and cut it out! Cut a long enough portion of the arc so that there will be an overlap of a few inches (you have the circumferences...). Take it up to the mast and make a trial fit, arranging things so that the overlap is at the back of the mast.

If your mast is not a circular cross section, the top and bottom edges will be wavy instead of straight. Put on the hose clamps top and bottom, and adjust everything as necessary for a nice fit. Using a ballpoint pen, mark at the edges of the hose clamps to get a straight line. Pull off the boot and cut at the line you just marked. When you reinstall the boot, it will now have an even top and bottom.

Do not neglect the seam at the back where the two ends of the boot overlap - it needs to be sealed, or rain water will still find its way below. We used 3M 5200 - it works great!

Finally, seal the top edge to the mast with rigging tape.  Update:  We've found that aluminum tape is a better answer for sealing the top edge.

Now you have a traditional and functional seal between the mast and the deck. Pour yourself a grog, and feel the fellowship of shipwrights who have done this very same task for centuries - you've earned it. Arrrr.

How To Cut a Mast Boot